Dewaxing hydrocarbon oil



Jan. 12, 1937. R E MANLEY 2,067,198

DEwAxING HYDRocARoN oIL Filed July 25, 1951 SL06!! WHA JNVENTOR A TT ORNE Y Patented Jan. 12, 1937 UNITED STATES PATENT OFFICE 2,067,198 nEwAxnvG HYDRooAnBoN olL Robert E. Manley, Port Arthur, Tex., assigner to The Texas Company, New York, N. Y., a corporation of Delaware This invention relates to dewaxing hydrocar- A bon oil, and more particularly to an improved process of removing parain wax from waxearl ing petroleum oil for the production of low pour test lubricating oil.

The invention broadly contemplates a process of dewaxing hydrocarbon oil wherein the oil is mixed with a liquid which is miscible therewith, suitable as a wax precipitating medium and having properties which adapt it ,for use as a refrigerant'and cooling the resulting mixture to eiect precipitation of the "wax constituentsby refrigeratively Ievaporating the diluent liquid from the liltered dewaxed liquid mixture while in indirect thermal contact with the fresh wax-bearing oil mixture. i

My invention contemplates diluting wax-bearing oil with a light hydrocarbon liquid composed substantially of propane and butane and in suit- '20 able proportion with the oil to produce a solution from which the wax constituents may be readily precipitated upon cooling. The liquid mixture is introduced to suitable chilling means wherein it undergoes cooling to precipitate the wax constituents, following which the cooled mixture is filtered to remove the precipitated wax from the diluteoil in the form of a slack wax cake.

The cooled dewaxed liquid mixture is then conducted into chilling means in indirect thermal 30 contact with the fresh dilute wax-bearing oil iiowing therethrough and the diluent liquid is evaporated from the dewaxed mixture with refrigerative effect, thereby moving the diluent liquid and simultaneously cooling the fresh waxbearing oil. If desired, and in order to further precipitate the wax constituents to the desired degree, the mixture may be further cooled by passing it through additional chilling means wherein a portion of the liquid propane and bu- 40 tane by itself may be vaporized as a refrigerant while out of direct thermal contact with the mixture.

The remaining diluent liquid retained in the dewaxed oil mixture which has been subjected to evaporation as well as that retained in the slack wax cake, is recovered for use in treating further oil by separately subjecting thedewaxed oil mixture and slack wax to warming or heating.

In the prior art methods of dewaxing oil, the

oil is diluted with petroleum naphtha, or with some other miseible liquid having substantially little solvent action upon the solid wax constituents,- andthe resultingmixture' chilled by passing it inindirect'heat exchange relationship with a refrigerating medium, such as brine, following which the chilled mirture is subjected to filtration to remove the precipitated wax constituents. This type vof operation necessitates the employ-l yment of virtually two distinct systems; namely,

one devoted to the actual removal of the wax -5 constituents from the dilute oil; and the other devoted to supplying brine at a low temperature for use in connection with the .dewaxing operation. Dewaxing systems required for this metho'd of operation are necessarily extensive and 1o complicated, and considerable'cash outlay is required to provide the necessary apparatus and v equipment.

The object of my invention, therefore, is to provide a single unitary dewaxing system where- 15 in I employ a liquid material combining the properties of a wax precipitating medium with those of a refrigerating medium, thereby avoiding the necessity of employing brine a's a cooling medium, and, at the same time, effecting better heat econ- 20 omy as well as greatly simplifying the entire operation.

In order to more fully disclose the invention. reference willnow be made to the accompanying iiow diagram illustrating diagrammatieally an 25 arrangement of flow adapted to carry out my invention. Y v

Wax-bearing oil, from a source notv shown, is delivered by a pump l to a dilution tank 2 wherein it is mixed with a diluent liquid received 30 from a source to be described later. The dilution tank 2 is adapted to withstand pressure so' as to permit maintaining the diluent and refrigerating material under suicient pressure to prevent volatilization. From the tank 2 the dilute 35 mixture is delivered to achilling or cooling means 3 wherein it is cooled as a result of indirect thermal contact'with the evaporating dewaxed mixture, as will shortly be described inmore detail.

If necessary, the mixture may be conducted 4Q from the cooler 3, through an additional or secondary cooling means Il, preferably of the type into which the refrigerant material may be directly expanded, out of contact with the liquid mixture undergoing cooling, in order to produce 45 the necessary reirigerative effect. After being subjected to whatever further cooling may be desired, the dilute mixture is introduced to a tank 5, still maintained under pressure wherein it may be mixed if desired with filter-aid material which 50 may be introduced to the tank in the form of a slurry from a tank 5a. A

The cooled liquid mixture containing precipitatedl wax is then introduced from the tank 5 to a lter press 6, advantageously ofthe rotating leaf 55 fresh dilute mixture is owing is sufficiently low to the liquid form for further use to permit expansion of the dewaxed mixture entering through the valve I0, thereby resulting in the evaporation of the light diluent hydrocarbon from the mixture under such conditions that the heat necessaryfor vaporization is absorbed from the relatively warmer and fresh mixture owing through the coils within the cooler 3. The diluent liquid vaporizing from the dewaxed mixture may be withdrawn from the evaporator chamber through a valve ll by means of which, in conjunction with the valve I0, the pressure within the evaporator chamber and, therefore, the extent of vaporization therewithin may be regullated. This vaporized material is conducted through a line l2 to a compressing means i3,

wherein it is converted into a liquid condition and then delivered through a cooler i4 to a pressure storage tank l5. A subatmospheric pressure may be maintained within the evaporator chamber by applying vacuum thereto with the compressor i3.k

The dewaxed mixture from which substantially all or onlya portion of the diluent liquid may be evaporated is withdrawn from the evaporator i chamber of the cooler 3 by a pump I6, and deliv- -ered to a stripping still l1 wherein it is subjected to heatingor warming in order to vaporize the remaining retained diluent liquid.v This stripping is preferablycarried out under pressure so that the evolved vapors will be completely condensed upon cooling in a condenser i8; otherwisel recompression of the cooled vapors is necessary. The condensed diluent material is .then conducted to the pressure storage tank l5 already referred to. The stripped dewaxed oil may be collected in a storage tank i9 for further disposition as may be desired.

The slack wax filter cake resulting from the filtering operation is ,delivered by a pump or other suitable displacing means 20 to a stripping still 2l wherein it is subjected towarming or heating to drive oi the retained diluent liquid hydrocarbon material in substantially the same manner described in connection with the stripping of the dewaxed oil mixture. vIhe vaporized material is conducted -to a cooler and condenser 22 and the condensate from there is delivered to the pressure storage tank i5, while the stripped slack wax may be withdrawn from the still to a tank 23.

The diluent liquid may be delivered as desired from the tank l5 by a pump 24 through a pipe 25 and valve 2S to the`dilution tank 2 for use in mixing with fresh wax-bearing oil as previously described. A suitable portion of the liquid may also be delivered through a pipe 21 and valve 28 to the cooler #l for direct expansion therein on the evaporative or refrigerant side in order to effect the desired amount of additional cooling of dilute wax-bearing mixture. The resulting vapor is withdrawn through a valve 29 into the pipe l2 previously referred to and leading to the compresser i3 by which means it i`s converted again eitherl as a diluent or as a refrigerant.

. tank, as Well as on the rest of the system, will depend, of course, upon the proportion of propane in the diluent.

The resulting mixture at a temperature of around F. is conducted through the coils of the cooler 3 wherein, due to the indirect thermal contact with the evaporating dewaxed mixture in contact with the exterior surfaces of the coils, it may be cooled to a temperature of around 40 F. or lower. The cooled mixture is then passed through chilling means fi wherein it may be furj yther cooled to a temperature of 25 F. The

chilled mixture is then delivered to the pressure lter 8 wherein it is filtered under a pressure of around pounds to remove the precipitated Wax in the form of a filter cake.

The resulting filter cake may be subjected to Washing with fresh diluent liquid followed, if desired, by blowing with an inert gas in order to displace the greater portion of retained oil other- Wise adhering to the cake.

'I'he filtrate, consisting of dewaxed oil and diluent liquid at a temperature of around 20 F., is collected in the tank 1 maintained under pressure to avoid vaporization of the diluent material, and

from there delivered to the interior of the evaporator chamber of the cooler 3 which is maintained under a pressure of around atmospheric. The vaporized material is removed from the evaporator chamber, compressed, cooled and delivered to the liquid storage tank l5. The remaining mixture of unvaporized diluent Aand dewaxed lubricating oil is continuously withdrawn from the evaporator chamber and introduced to the strippingstill I'l wherein it may be heated to a temperature ranging from 200 to 300 F. under a pressure of around pounds, thereby vaporizing the retained propane and butane. The vaporized material is conducted under pressure to the condenser I8 and delivered from there in the form of a liquid to the pressure storage tank l5 for further use. The diluent free lubricating oil having a pour test of 0 F. or lower may be withdrawn from the stripping still for further treatment as may be desired.

The slack wax filter cake, which may contain a substantial quantity of retained diluent liquid, is subjected to heating under conditions of pressure and temperature substantially similar to those employed in stripping the filtrate or dewaxed oil in order to remove the retained light material which may also be condensed under pressure and delivered in liquid form to the pressure storage tank l5.

While certain operating conditions have been described in the foregoing example, it is contemplated that these conditions, particularly as regards temperature and pressure, may be varied to suit different requirements. Also While the use of propane and butane has been described, other light'hydrocarbons, such as Vpropylene, butylene and i'the like, having refrigerant properties as Well as being suitable as wax precipitating media, may alsojbe employed.

Obviously many `modifications and variations of the'invention, as hereinbefore set forth, may

be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim: p

l. The process of dewaxing mineral lubricating oil comprising mixing wax-bearing oil with a volatile petroleum fraction of the character of propane and butane, chilling the mixture to a temperature of the order of 0 F. and below to solidify the wax, introducing the cold dilute mixture while under superatmospheric pressure to pressure iiltering means, forming therein a filter cake of solid wax, continuously removing from the lter means a stream of dewaxed ltrate, and imposing sumcient pressure upon said ltrate stream during removal from the ltering means to prevent substantial vaporization of the diluent from the oil during ltration.

2. The process of dewaxing mineral lubricating oil comprising mixing wax-bearing oil with a diluent comprising propane, chilling the mixture to a temperature of the order of 0 F. and below to solidify the wax, introducing the cold dilute trate, and imposing sufficient pressure upon said filtrate stream during removal from the filtering means to prevent substantial vaporization of the diluent from the oil during filtration.

3. The process of dewaxing mineral lubricating oil comprising mixing wax-bearing oil with a liqueed hydrocarbon diluent having a vapor pressure corresponding substantially to that of propane and butane, chilling themixture to a temperature of the order of 0 F. and below to solidify the wax, introducing the cold dilute mixture while under superatmosphericpressure to pressure filtering means, forming therein a filter cake of solid wax, continuously removing from the filter means a stream of dewaxed filtrate, and imposing sumcient pressure upon said iiltrate stream during removal from the filtering means to prevent substantial vaporization of the diluent from the oil during filtration.

4. The process of dewaxing mineral lubricating oil comprising mixing wax-bearing oil with a liqueiied normally gaseous diluent, chilling the mixture to a temperature of the order of 0 F. and below to solidify the wax, introducing the cold dilute mixture While under superatmospheric pressure to pressure filtering means, forming therein a lter cake of solid wax, continuously removing from the filter means a stream of dewaxed filtrate, and imposing sufficient pressure upon said filtrate stream during removal from the filtering means to prevent substantial vaporization of the diluent from the oil during filtration.

ROBERT E. MANLEY. 

